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  <title>对 JSON 格式的字符串进行解码</title>
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 <body class="docs"><div id="layout">
  <div id="layout-content"><div id="function.json-decode" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">json_decode</h1>
  <p class="verinfo">(PHP 5 &gt;= 5.2.0, PHP 7, PECL json &gt;= 1.2.0)</p><p class="refpurpose"><span class="refname">json_decode</span> &mdash; <span class="dc-title">对 JSON 格式的字符串进行解码</span></p>

 </div>
 
 <div class="refsect1 description" id="refsect1-function.json-decode-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="methodname"><strong>json_decode</strong></span>
    ( <span class="methodparam"><span class="type">string</span> <code class="parameter">$json</code></span>
   [, <span class="methodparam"><span class="type">bool</span> <code class="parameter">$assoc</code><span class="initializer"> = false</span></span>
   [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$depth</code><span class="initializer"> = 512</span></span>
   [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$options</code><span class="initializer"> = 0</span></span>
  ]]] ) : <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span></div>

  <p class="para rdfs-comment">
   接受一个 JSON 编码的字符串并且把它转换为 PHP 变量
  </p>
 </div>

 
 <div class="refsect1 parameters" id="refsect1-function.json-decode-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<code class="parameter">json</code></dt>

     <dd>

      <p class="para">
       待解码的 <code class="parameter">json</code> <span class="type"><a href="language.types.string.html" class="type string">string</a></span> 格式的字符串。
      </p>
      <p class="para">
       这个函数仅能处理 UTF-8 编码的数据。
      </p>
      
 <blockquote class="note"><p><strong class="note">Note</strong>: 
  <p class="para">
   PHP implements a superset of JSON as specified in the original
   <a href="http://www.faqs.org/rfcs/rfc7159" class="link external">&raquo;&nbsp;RFC 7159</a>.
  </p>
 </p></blockquote>

     </dd>

    
    
     <dt>
<code class="parameter">assoc</code></dt>

     <dd>

      <p class="para">
       当该参数为 <strong><code>TRUE</code></strong> 时，将返回 <span class="type"><a href="language.types.array.html" class="type array">array</a></span> 而非 <span class="type"><a href="language.types.object.html" class="type object">object</a></span> 。
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">depth</code></dt>

     <dd>

      <p class="para">
       指定递归深度。
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">options</code></dt>

     <dd>

      <p class="para">
       JSON解码的掩码选项。 现在有两个支持的选项。
       第一个是<strong><code>JSON_BIGINT_AS_STRING</code></strong>，
       用于将大整数转为字符串而非默认的float类型。第二个是
       <strong><code>JSON_OBJECT_AS_ARRAY</code></strong>，
       与将<code class="parameter">assoc</code>设置为 <strong><code>TRUE</code></strong> 有相同的效果。
      </p>
     </dd>

    
   </dl>

  </p>
 </div>

 
 <div class="refsect1 returnvalues" id="refsect1-function.json-decode-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   Returns the value encoded in <code class="parameter">json</code> in appropriate
   PHP type. Values <em>true</em>, <em>false</em> and
   <em>null</em> are returned as <strong><code>TRUE</code></strong>, <strong><code>FALSE</code></strong> and <strong><code>NULL</code></strong>
   respectively. <strong><code>NULL</code></strong> is returned if the <code class="parameter">json</code> cannot
   be decoded or if the encoded data is deeper than the recursion limit.
  </p>
 </div>

 
 <div class="refsect1 examples" id="refsect1-function.json-decode-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-4513">
    <p><strong>Example #1 <span class="function"><strong>json_decode()</strong></span> 的例子</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$json&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'{"a":1,"b":2,"c":3,"d":4,"e":5}'</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">json_decode</span><span style="color: #007700">(</span><span style="color: #0000BB">$json</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">json_decode</span><span style="color: #007700">(</span><span style="color: #0000BB">$json</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">true</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

    <div class="example-contents"><p>以上例程会输出：</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
object(stdClass)#1 (5) {
    [&quot;a&quot;] =&gt; int(1)
    [&quot;b&quot;] =&gt; int(2)
    [&quot;c&quot;] =&gt; int(3)
    [&quot;d&quot;] =&gt; int(4)
    [&quot;e&quot;] =&gt; int(5)
}

array(5) {
    [&quot;a&quot;] =&gt; int(1)
    [&quot;b&quot;] =&gt; int(2)
    [&quot;c&quot;] =&gt; int(3)
    [&quot;d&quot;] =&gt; int(4)
    [&quot;e&quot;] =&gt; int(5)
}
</pre></div>
    </div>
   </div>
   <div class="example" id="example-4514">
    <p><strong>Example #2 Accessing invalid object properties</strong></p>
    <div class="example-contents"><p>
     Accessing elements within an object that contain characters not
     permitted under PHP&#039;s naming convention (e.g. the hyphen) can be
     accomplished by encapsulating the element name within braces and the apostrophe.
    </p></div>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br />$json&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'{"foo-bar":&nbsp;12345}'</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">$obj&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">json_decode</span><span style="color: #007700">(</span><span style="color: #0000BB">$json</span><span style="color: #007700">);<br />print&nbsp;</span><span style="color: #0000BB">$obj</span><span style="color: #007700">-&gt;{</span><span style="color: #DD0000">'foo-bar'</span><span style="color: #007700">};&nbsp;</span><span style="color: #FF8000">//&nbsp;12345<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

   </div>
   <div class="example" id="example-4515">
    <p><strong>Example #3 common mistakes using <span class="function"><strong>json_decode()</strong></span></strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br /></span><span style="color: #FF8000">//&nbsp;the&nbsp;following&nbsp;strings&nbsp;are&nbsp;valid&nbsp;JavaScript&nbsp;but&nbsp;not&nbsp;valid&nbsp;JSON<br /><br />//&nbsp;the&nbsp;name&nbsp;and&nbsp;value&nbsp;must&nbsp;be&nbsp;enclosed&nbsp;in&nbsp;double&nbsp;quotes<br />//&nbsp;single&nbsp;quotes&nbsp;are&nbsp;not&nbsp;valid&nbsp;<br /></span><span style="color: #0000BB">$bad_json&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">"{&nbsp;'bar':&nbsp;'baz'&nbsp;}"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">json_decode</span><span style="color: #007700">(</span><span style="color: #0000BB">$bad_json</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;null<br /><br />//&nbsp;the&nbsp;name&nbsp;must&nbsp;be&nbsp;enclosed&nbsp;in&nbsp;double&nbsp;quotes<br /></span><span style="color: #0000BB">$bad_json&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'{&nbsp;bar:&nbsp;"baz"&nbsp;}'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">json_decode</span><span style="color: #007700">(</span><span style="color: #0000BB">$bad_json</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;null<br /><br />//&nbsp;trailing&nbsp;commas&nbsp;are&nbsp;not&nbsp;allowed<br /></span><span style="color: #0000BB">$bad_json&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'{&nbsp;bar:&nbsp;"baz",&nbsp;}'</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">json_decode</span><span style="color: #007700">(</span><span style="color: #0000BB">$bad_json</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;null<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

   </div>
   <div class="example" id="example-4516">
    <p><strong>Example #4 <code class="parameter">depth</code> errors</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">//&nbsp;Encode&nbsp;the&nbsp;data.<br /></span><span style="color: #0000BB">$json&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">json_encode</span><span style="color: #007700">(<br />&nbsp;&nbsp;&nbsp;&nbsp;array(<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">1&nbsp;</span><span style="color: #007700">=&gt;&nbsp;array(<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'English'&nbsp;</span><span style="color: #007700">=&gt;&nbsp;array(<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'One'</span><span style="color: #007700">,<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'January'<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">),<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'French'&nbsp;</span><span style="color: #007700">=&gt;&nbsp;array(<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'Une'</span><span style="color: #007700">,<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">'Janvier'<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #007700">)<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;)<br />&nbsp;&nbsp;&nbsp;&nbsp;)<br />);<br /><br /></span><span style="color: #FF8000">//&nbsp;Define&nbsp;the&nbsp;errors.<br /></span><span style="color: #0000BB">$constants&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">get_defined_constants</span><span style="color: #007700">(</span><span style="color: #0000BB">true</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$json_errors&nbsp;</span><span style="color: #007700">=&nbsp;array();<br />foreach&nbsp;(</span><span style="color: #0000BB">$constants</span><span style="color: #007700">[</span><span style="color: #DD0000">"json"</span><span style="color: #007700">]&nbsp;as&nbsp;</span><span style="color: #0000BB">$name&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #0000BB">$value</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;if&nbsp;(!</span><span style="color: #0000BB">strncmp</span><span style="color: #007700">(</span><span style="color: #0000BB">$name</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"JSON_ERROR_"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">11</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$json_errors</span><span style="color: #007700">[</span><span style="color: #0000BB">$value</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #0000BB">$name</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;}<br />}<br /><br /></span><span style="color: #FF8000">//&nbsp;Show&nbsp;the&nbsp;errors&nbsp;for&nbsp;different&nbsp;depths.<br /></span><span style="color: #007700">foreach&nbsp;(</span><span style="color: #0000BB">range</span><span style="color: #007700">(</span><span style="color: #0000BB">4</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">3</span><span style="color: #007700">,&nbsp;-</span><span style="color: #0000BB">1</span><span style="color: #007700">)&nbsp;as&nbsp;</span><span style="color: #0000BB">$depth</span><span style="color: #007700">)&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">json_decode</span><span style="color: #007700">(</span><span style="color: #0000BB">$json</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">true</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$depth</span><span style="color: #007700">));<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'Last&nbsp;error:&nbsp;'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$json_errors</span><span style="color: #007700">[</span><span style="color: #0000BB">json_last_error</span><span style="color: #007700">()],&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

    <div class="example-contents"><p>以上例程会输出：</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
array(1) {
  [1]=&gt;
  array(2) {
    [&quot;English&quot;]=&gt;
    array(2) {
      [0]=&gt;
      string(3) &quot;One&quot;
      [1]=&gt;
      string(7) &quot;January&quot;
    }
    [&quot;French&quot;]=&gt;
    array(2) {
      [0]=&gt;
      string(3) &quot;Une&quot;
      [1]=&gt;
      string(7) &quot;Janvier&quot;
    }
  }
}
Last error: JSON_ERROR_NONE

NULL
Last error: JSON_ERROR_DEPTH
</pre></div>
    </div>
   </div>
   <div class="example" id="example-4517">
    <p><strong>Example #5 <span class="function"><strong>json_decode()</strong></span> of large integers</strong></p>
    <div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$json&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'{"number":&nbsp;12345678901234567890}'</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">json_decode</span><span style="color: #007700">(</span><span style="color: #0000BB">$json</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">json_decode</span><span style="color: #007700">(</span><span style="color: #0000BB">$json</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">false</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">512</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">JSON_BIGINT_AS_STRING</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
    </div>

    <div class="example-contents"><p>以上例程会输出：</p></div>
    <div class="example-contents screen">
<div class="cdata"><pre>
object(stdClass)#1 (1) {
  [&quot;number&quot;]=&gt;
  float(1.2345678901235E+19)
}
object(stdClass)#1 (1) {
  [&quot;number&quot;]=&gt;
  string(20) &quot;12345678901234567890&quot;
}
</pre></div>
    </div>
   </div>
  </p>
 </div>

 
 <div class="refsect1 notes" id="refsect1-function.json-decode-notes">
  <h3 class="title">注释</h3>
  <blockquote class="note"><p><strong class="note">Note</strong>: 
   <p class="para">
    The JSON spec is not JavaScript, but a subset of JavaScript.
   </p>
  </p></blockquote>
  <blockquote class="note"><p><strong class="note">Note</strong>: 
   <p class="para">
    In the event of a failure to decode, <span class="function"><a href="json_last_error.html" class="function">json_last_error()</a></span>
    can be used to determine the exact nature of the error.
   </p>
  </p></blockquote>
 </div>

 
 <div class="refsect1 changelog" id="refsect1-function.json-decode-changelog">
  <h3 class="title">更新日志</h3>
  <p class="para">
   <table class="doctable informaltable">
    
     <thead>
      <tr>
       <th>版本</th>
       <th>说明</th>
      </tr>

     </thead>

     <tbody class="tbody">
      <tr>
       <td>7.1.0</td>
       <td>
        An empty JSON key (&quot;&quot;) can be encoded to the empty object property
        instead of using a key with value <em>_empty_</em>.
       </td>
      </tr>

      <tr>
       <td>7.0.0</td>
       <td>
        Rejected RFC 7159 incompatible number formats - top level
        (07, 0xff, .1, -.1) and all levels ([1.], [1.e1])
       </td>
      </tr>

      <tr>
       <td>7.0.0</td>
       <td>
        An empty PHP string or value that after casting to string is an empty
        string (<em>NULL</em>, <em>FALSE</em>) results
        in JSON syntax error.
       </td>
      </tr>

     <tr>
       <td>5.6.0</td>
       <td>
        Invalid non-lowercased variants of the <em>true</em>,
        <em>false</em> and <em>null</em> literals are no
        longer accepted as valid input, and will generate warnings.
       </td>
      </tr>

      <tr>
       <td>5.4.0</td>
       <td>
        The <code class="parameter">options</code> parameter was added.
       </td>
      </tr>

      <tr>
       <td>5.3.0</td>
       <td>Added the optional <code class="parameter">depth</code>. The default recursion depth was increased from 128 to 512</td>
      </tr>

      <tr>
       <td>5.2.3</td>
       <td>The nesting limit was increased from 20 to 128</td>
      </tr>

      <tr>
       <td>5.2.1</td>
       <td>
        Added support for JSON decoding of basic types.
       </td>
      </tr>

     </tbody>
    
   </table>

  </p>
 </div>

 
 <div class="refsect1 seealso" id="refsect1-function.json-decode-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="json_encode.html" class="function" rel="rdfs-seeAlso">json_encode()</a> - 对变量进行 JSON 编码</span></li>
    <li class="member"><span class="function"><a href="json_last_error.html" class="function" rel="rdfs-seeAlso">json_last_error()</a> - 返回最后发生的错误</span></li>
   </ul>
  </p>
 </div>

</div></div></div></body></html>